Old Dominion University ODU Digital Commons Biological Sciences Theses & Dissertations Biological Sciences Summer 2018 The Importance of Keeping the Big Ones: Harvest Slot Limits and Marine Protected Areas for the Management of the Caribbean Spiny Lobster Gayathiri Gnanalingam Old Dominion University, [email protected] Follow this and additional works at: https://digitalcommons.odu.edu/biology_etds Part of the Aquaculture and Fisheries Commons, Ecology and Evolutionary Biology Commons, and the Natural Resources Management and Policy Commons Recommended Citation Gnanalingam, Gayathiri. "The Importance of Keeping the Big Ones: Harvest Slot Limits and Marine Protected Areas for the Management of the Caribbean Spiny Lobster" (2018). Doctor of Philosophy (PhD), Dissertation, Biological Sciences, Old Dominion University, DOI: 10.25777/hhrk-9p92 https://digitalcommons.odu.edu/biology_etds/31 This Dissertation is brought to you for free and open access by the Biological Sciences at ODU Digital Commons. It has been accepted for inclusion in Biological Sciences Theses & Dissertations by an authorized administrator of ODU Digital Commons. For more information, please contact [email protected]. THE IMPORTANCE OF KEEPING THE BIG ONES: HARVEST SLOT LIMITS AND MARINE PROTECTED AREAS FOR THE MANAGEMENT OF THE CARIBBEAN SPINY LOBSTER by Gayathiri Gnanalingam BSc August 2008, Otago University, New Zealand LLB August 2008, Otago University, New Zealand MSc December 2013, Otago University, New Zealand A Dissertation Submitted to the Faculty of Old Dominion University in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY ECOLOGICAL SCIENCES OLD DOMINON UNIVERSITY August 2018 Approved by: Mark J. Butler, IV (Director) Holly Gaff (Member) Alison MacDiarmid (Member) ABSTRACT THE IMPORTANCE OF KEEPING THE BIG ONES: HARVEST SLOT LIMITS AND MARINE PROTECTED AREAS FOR THE MANAGEMENT OF THE CARIBBEAN SPINY LOBSTER Gayathiri Gnanalingam Old Dominion University, 2018 Director: Dr. Mark J. Butler IV Fishing typically removes the oldest and/or largest individuals from populations undermining stability and reproductive success. Traditional fisheries management tools fail to protect these oldest and/or largest individuals, but two less conventional tools: marine protected areas (MPAs), and harvest slot limits have the potential to do so. Here I tested the possible use of these tools for the Caribbean spiny lobster, Panulirus argus, an iconic and economically valued species. After decades of intense fishing, the largest lobsters have largely been wiped out. The loss of the largest lobsters is significant as large lobsters have considerably greater reproductive potential than their smaller counterparts. I had four main objectives (1) developing a technique for directly ageing P. argus using banding in the gastric ossicles, (2) examining the possibility of reproductive senescence as it relates to body size in P. argus, (3) modeling the potential use of harvest slot limits and MPAs using a two-sex stage-structured matrix model, and (4) assessing the possible ecological consequences in terms of interactions with prey-species, of increasing the abundance and size of P. argus through a series of cafeteria trials. This work provides some necessary background information to support using MPAs and harvest slot limits in the management of P. argus in the Caribbean - calls for which has grown appreciably in recent years. Direct ageing of P. argus using bands in the gastric ossicles proved successful as it was possible to validate the ages of wild caught lobsters with lobsters of known age. The success of this technique opens up the potential for age based stock assessment and consideration of the relationship between size, age and reproduction. Lobsters were not found to exhibit reproductive senescence and for several of the metrics tested there was a positive relationship with parental size, confirming the biological value of retaining the largest lobsters in populations. The modeling demonstrated clearly the potential for MPAs and slot limits combined to increase the sizes and densities of P. argus in the marine environment, while the cafeteria trials demonstrated that larger lobsters did not have any appreciable preference for species of high ecological value. iv Copyright, 2018, by Gayathiri Gnanalingam, and Mark J. Butler IV, All Rights Reserved v ACKNOWLEDGMENTS There is no way that this dissertation would have been completed without the help of a number of wonderfully generous and patient people. First I would like to thank my major advisor Mark Butler. It was a chance meeting on the rocky coast of East Otago New Zealand that led to this and I’m thankful for all the adventures that have followed. With his guidance, support and enthusiasm for science I have become a better scientist, (not to mention plumber, and brick mover). I look forward to more (rum inspired) late night debates and story tellings in the future. Thank you to my committee members: Holly Gaff who graciously held my hand through the modeling work and Alison MacDiarmid who always gave thoughtful advice and much appreciated insight on all aspects of this research. Thank you also to Kent Carpenter and Dan Barshis who provided guidance early on. To my ODU labmates past and present, your help was invaluable and without it, there is no way this could have been done. Jason Spadaro, Casey Butler, Jack Butler and Ben Gutzler, you guys showed me how to catch lobsters (key), set up aquaria, handle the boats and trailers, and rescued me from the water on more than one occasion (shark encounter included). Thank you for answering my inane questions on all manner of things and for not making too much fun of my accent or choice of vocabulary. Labmates Emily Anderson, Sam Hagedorn and Marla Valentine thanks also for your help along the way. Many thanks to our UF colleagues, in particular: Abby Clark, Devon Pharo and Nate Berkebile, your help in the field was always appreciated especially those times that I was in the Keys by myself. To the friendly folks in the lobster team at the Florida Wildlife Commission in Marathon, thank you for being gracious hosts for the bulk of the lab work in this dissertation. Tom Matthews, Emily Hutchinson, Gabby Renchen, and Maria Cooksey – you have been amazing vi collaborators and friends. The ageing work in particular could not have been done without you. I would also like to acknowledge the help of the Center for Quantitative Fisheries Ecology at ODU for allowing me to work in their lab and showing me the ropes on how to process samples for the lobster ageing work. Many thanks to organizations that helped fund this research. In particular, Fulbright New Zealand and PEO. Without Fulbright’s support I would not have even considered graduate study in the US. PEO did not just help fund this research, but the wonderful women of this organization opened up their homes to me and constantly checked in on my wellbeing the whole time I was in the US. Finally, I would like to thank my friends and family. In the US I found a group of exceptionally welcoming and generous people who looked after me and made sure I was ok. I look forward to catching up with you again soon. To my family in New Zealand, thank you for your continued support. Amma, Appa and Anna, thank you for always encouraging and supporting me in everything I have chosen to do, even if it meant traveling to the other side of the world to do it. vii TABLE OF CONTENTS Page LIST OF TABLES ..................................................................................................................... ix LIST OF FIGURES .................................................................................................................... x Chapter 1. INTRODUCTION 1.1 GENERAL INTRODUCTION ................................................................................. 1 1.2 REPRODUCTION IN MARINE ORGANISMS ..................................................... 1 1.3 CONSERVING SPAWNING STOCK .................................................................... 6 1.4 THE CARIBBEAN SPINY LOBSTER ................................................................. 10 2. DIRECT AGEING 2.1 INTRODUCTION .................................................................................................. 18 2.2 METHODS ............................................................................................................. 20 2.3 RESULTS ............................................................................................................... 25 2.4 DISCUSSION ......................................................................................................... 33 3. REPRODUCTIVE SENESCENCE 3.1 INTRODUCTION .................................................................................................. 38 3.2 METHODS ............................................................................................................. 43 3.3 RESULTS ............................................................................................................... 50 3.4 DISCUSSION ......................................................................................................... 60 4. MODELING MPAS AND HARVEST SLOT LIMITS 4.1 INTRODUCTION .................................................................................................. 68 4.2 METHODS ............................................................................................................. 72 4.3 RESULTS ..............................................................................................................